1. Field of the Invention
The present invention relates to a video-signal output apparatus having a function of scrambling a video signal and outputting the signal, a video-signal input apparatus having a function of descrambling an input scrambled video signal, a scrambling method for the output apparatus, and a descrambling method for the input apparatus.
2. Description of the Related Art
In many cases, video software, such as movies, is prohibited from being copied beyond private use in accordance with copyright law. To protect the copyright of the video software, copy-control information is often superimposed at a predetermined position in a video signal in the video software.
Regarding a position at which the copy-control information should be inserted, the copy-control information is, in general, inserted in, for example, a predetermined horizontal scanning interval in a vertical blanking interval.
The value of the copy-control information indicates that the video software may be copied freely, is permitted to be copied to only one generation, or is prohibited from being copied.
Assuming that a video signal from a video source in which copy-control information indicating permission for only-one-generation copying is superimposed on the signal, is recorded (copied) on a recording medium by a recording apparatus, the recording apparatus performs recording after rewriting the copy-control information from a value indicating permission for only-one-generation copying to a value indicating prohibition of copying.
By way of example, when the recording medium that contains the copy-prohibited video source is read and copied, the recording apparatus detects the copy-control information, superimposed on the video signal, which indicates prohibition of copying, and operates so as not to perform recording on the recording medium. In other words, the use of the copy-control information prevents an unauthorized act of copying.
In actuality, it is always possible that the above-described copy-control information may be falsified by an unscrupulous person.
By way of example, by providing an apparatus that eliminates or modifies copy-control information so as to indicate that is xe2x80x9ccopy freelyxe2x80x9d or xe2x80x9cpermission for only-one-generation copyingxe2x80x9d between an output apparatus for outputting a video signal from a video source and a recording apparatus for recording an input video signal, the video source can be copied without limit.
Technology for falsifying the copy-control information is very easily realized since the copy-control information is simply a superimposed signal in a vertical blanking interval of the video signal.
In addition, in a recording apparatus for recording an input video signal from a video source, by only detecting the condition (waveform) of the input video signal, it is difficult to determine whether the copy-control information has been actually falsified, since superimposition of the copy-control information is a simple technique.
Accordingly, it is an object of the present invention to provide a video-signal output apparatus, a video-signal input apparatus, a scramble apparatus, and a descramble apparatus which protect the copyrights of video sources, even for cases where copy-control information has been intentionally falsified.
To this end, according to an aspect of the present invention, the foregoing object is achieved through provision of a video-signal output apparatus including: a signal-scrambling unit for scrambling, in accordance with a predetermined method, video signals on which copy-control information is superimposed at a predetermined position in a vertical blanking interval, and for performing scramble processing for one field or one frame interval so that the signal-scrambling unit performs scramble processing for at least an effective screen interval and that the signal-scrambling unit performs no scramble processing at a position at which at least the copy-control information is superimposed in the vertical blanking interval; and an output unit for outputting video signals processed by the signal-scrambling unit to the exterior.
According to another aspect of the present invention, the foregoing object is achieved through provision of a video-signal output apparatus including: a copy-control-information detecting unit for detecting copy-control information superimposed on a video signal at a predetermined position in a vertical blanking interval; a scramble-key generating unit for generating a scramble key by using the copy-control information detected by the copy-control-information detecting unit; a signal-scrambling unit for scrambling the video signal, based on the scramble key generated by the scramble-key generating unit in accordance with a predetermined method; and an output unit for outputting the video signal processed by the signal-scrambling unit to the exterior.
Preferably, the signal-scrambling unit performs scramble processing for one field or one frame interval so that the signal-scrambling unit performs scramble processing for at least an effective screen interval and that the signal-scrambling unit performs no scramble processing at a position at which at least the copy-control information is superimposed in the vertical blanking interval.
The video-signal output apparatus may further include a reading unit for performing reading and outputting on a predetermined recording medium on which video signals are recorded in a predetermined recording method. The video signals, read by the reading unit, are input to the signal-scrambling unit.
The copy-control information to be used by the scramble-key generating unit may be copy-control information superimposed on the video signals read and output by the reading unit, which are detected by the copy-control-information detecting unit.
According to a further aspect of the present invention, the foregoing object is achieved through provision of a video-signal input apparatus to which video signals are input and in which part of the video signals in an effective screen interval in at least one field or one frame interval is scrambled and in which part of the video signals in the interval of copy-control information at least superimposed at a predetermined position in a vertical blanking interval is not scrambled. The video-signal input apparatus includes a copy-control-information detecting unit for detecting the copy-control information, a scramble-key reproducing unit for reproducing a scramble key by using the copy-control information detected by the copy-control-information detecting unit; and a signal-descrambling unit for descrambling the input video signals, based on the scramble key reproduced by the scramble-key reproducing unit in accordance with a predetermined method.
Preferably, the video-signal input apparatus further includes a recording unit for recording the video signals processed by the signal-descrambling unit on a predetermined recording medium in accordance with a predetermined recording method.
According to a still further aspect of the present invention, the foregoing object is achieved through provision of a scramble method for scrambling, in accordance with a predetermined method, video signals on which copy-control information is superimposed at a predetermined position in a vertical blanking interval, and for performing scramble processing for one field or one frame interval so that the signal-scrambling unit performs scramble processing for at least an effective screen interval and that the signal-scrambling unit performs no scramble processing at a position at which at least the copy-control information is superimposed in the vertical blanking interval.
According to a further aspect of the present invention, the foregoing object is achieved through provision of a descramble method for descrambling video signals in which part of said video signals in an effective screen interval in at least one field or one frame interval is scrambled and in which part of said video signals in the interval of copy-control information at least superimposed at a predetermined position in a vertical blanking interval is not scrambled. The descramble method executes: a copy-control-information detecting process for detecting the copy-control information from the input video signal; a scramble-key reproducing process for reproducing a scramble key by using the copy-control information detected by the copy-control-information detecting process; and a signal-descramble process for descrambling the input video signal, based on the scramble key reproduced by the scramble-key reproducing process in accordance with a predetermined method.
According to a more aspect of the present invention, the foregoing object is achieved through provision of a descramble method for descrambling video signals in which part of said video signals in an effective screen interval in at least one field or one frame interval is scrambled and in which part of said video signals in the interval of copy-control information at least superimposed at a predetermined position in a vertical blanking interval is not scrambled. The descramble method executes: a copy-control-information detecting process for detecting the copy-control information from the input video signal; a scramble-key reproducing process for reproducing a scramble key by using the copy-control information detected by the copy-control-information detecting process; and a signal-descramble process for descrambling the input video signal, based on the scramble key reproduced by the scramble-key reproducing process in accordance with a predetermined method.
According to the present invention, in order to limit copying for the purpose of, for example, protection of copyright, scrambling or descrambling is performed based on a scramble key generated using copy-control information. Therefore, if the copy-control information has been falsified, a scramble key for scrambling does not coincide with a scramble key for descrambling, so that appropriate descrambling is not performed. In other words, an appropriately scramble-processed picture cannot be obtained for cases where the copy-control information is falsified, whereby strong prevention of falsification is achieved. By determining whether appropriate descrambling has been performed, detection of falsification is facilitated. When video signals are recorded or read using an inappropriate apparatus is not adapted for scrambling and descrambling functions in the present invention, an apparatus to which the video signals are input obtains an unclear picture. In this respect, protection of copying is enhanced.
According to the present invention, by performing scramble processing so that scrambling is performed in an effective screen interval in one field (frame) interval and that copy-control information inserted in a vertical blanking interval is not scrambled, the copy-control information can be easily detected regardless of whether the video signals have been descrambled. This can simplify a construction for a scrambling process according to the present invention, which is correlated with copy-control information.